Electric Fan / Relays / Switch Override - Defender Source
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  #1  
Old August 19th, 2011, 08:09 AM
jijalicious
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Jiman Khosravan
'94 D90
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Lightbulb Electric Fan / Relays / Switch Override

Morning D-World,

I'm trying to work on my electric fan problems...

In order to give myself a failsafe, in case the temp switch on the thermostat fails, I want to install an override switch to turn on the fan manually.

2 relays being used...

Relay 1 trigger: temp switch which then gives +12V to fan...

Relay 2 trigger: switch which then gives +12V to fan...


For the switch, I want to use a small source for the trigger, not directly from the battery. Any recommendations?

And attached is the diagram. sorry... used mspaint... anyone see any issues?

The fact that the fan + side is getting 2 signals from 2 different lcoations shoudn't be an issue right?

And if the points 87 on each relay gets a +12V from the OTHER relay shouldn't be a problem either right?

Thanks,

~Jij
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  #2  
Old August 19th, 2011, 09:00 AM
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John B.
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You only need one relay. The manual switch and the temperature switch can simply be in parallel on the input to the relay.
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Old August 19th, 2011, 09:27 AM
jijalicious
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Jiman Khosravan
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By going in parallel and giving the thermostat switch a +12V charge when it's not "active," won't mess up the sensor? Like water flownig upstream kinda thing?

I'm just being a moron right now aren't I?

~Jij

------ Follow up post added August 19th, 2011 09:43 AM ------

oh, right.. the main reason I want second relay is in case one relay dies, I have failover...

So no single point of failure.

But my question still stands, will giving it the sensor +12V when not active damage it?

And what's the recommended trigger to use on the switch? What's +12V and always ON on the car?

~Jij
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  #4  
Old August 19th, 2011, 09:51 AM
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Dro
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Jiman,

Save yourself all the headaches and buy the Flex-a-Lite Variable Speed Controller 33054.

You have the option of shutting it off (override) or turning it on (on-demand).

I ran it with my 4.6L DI w/dual electric fans.
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  #5  
Old August 19th, 2011, 10:12 AM
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mark kellgren
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Quote:
Originally Posted by rrc.swb View Post
Jiman,

Save yourself all the headaches and buy the Flex-a-Lite Variable Speed Controller 33054.

You have the option of shutting it off (override) or turning it on (on-demand).

I ran it with my 4.6L DI w/dual electric fans.
Just so everyone knows, I actually contacted flex-a-lite on those controllers when i was toying with the idea of going electric. Those controllers are not sealed and water-proof which means they may fail during water crossings. I know some have had good luck with them, but it's important to know the risks.

I have completely abandoned any thoughts on going electrics, as having just swapped out my head and then replacing a radiator, I find that it takes about 2 min literally to remove my mechanical fan since I have the proper long wrenches that I keep stowed away. that's not a lot of extra time for a deep ford that would require a reece on foot anyway and a block cool down.
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  #6  
Old August 19th, 2011, 10:33 AM
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John B.
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Quote:
Originally Posted by Overlander View Post
Just so everyone knows, I actually contacted flex-a-lite on those controllers when i was toying with the idea of going electric. Those controllers are not sealed and water-proof which means they may fail during water crossings. I know some have had good luck with them, but it's important to know the risks.
I'm been using an FAL controller for the last 5 years. Never had any problems. Driving though mud and water over the hood is a normal occurrence for me.

However, the best choice of controller out there is the DCControl unit. He was not selling to the public when I got my FAL unit. Fully waterproof, heavily overbuilt electrically.

http://www.dccontrol.com/fancontrol.htm

------ Follow up post added August 19th, 2011 08:35 AM ------

Quote:
Originally Posted by jijalicious View Post
But my question still stands, will giving it the sensor +12V when not active damage it?

And what's the recommended trigger to use on the switch? What's +12V and always ON on the car?

~Jij
No, it will not hurt the temperature switch.

I would used normal switched power as the source. No point having the fan running with the engine off.
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  #7  
Old August 19th, 2011, 02:33 PM
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Mike Doligalski
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Just a thought, but I know on my 90 turning on the blower motor to the first setting and the temp control all the way to the "warmest" setting will turn on the electric fan but not the compressor.
-M
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